Hard disks and other forms of persistent data storage are used to store data for arbitrarily long periods of time. When data is no longer needed, it may be deleted from persistent storage. Deletion is typically performed by configuring filesystem metadata to no longer make blocks of a file available to users in connection with that file. However, the underlying blocks containing the file data may be retained until the filesystem reuses them. In certain circumstances, organizations with high security needs may physically destroy or otherwise clean their discarded hard drives to ensure that secret data does not fall into the wrong hands.
In some examples, organizations run programs on host computers to securely delete entire filesystems containing sensitive data. Such secure deletion may involve writing random data over the entire volume multiple times, to remove traces of previous data that may have been left behind.